Monitoring of the generation of non-mutagenic benzoic acid compounds during the manufacture of erythrosine

The generation of 2-(2',4'-dihydroxybenzoyl) benzoic acid (DHBBA) and 2-(2',4'-dihydroxy-3',5'-diiodobenzoyl) benzoic acid (DHDIBBA) during the manufacture of erythrosine (Food Red No. 3) was examined. DHBBA is formed as an intermediate during the synthesis of fluorescein, and as fluorescein is produced, it is gradually consumed. However, under inappropriate reaction conditions, it remains in the resulting fluorescein at the termination of synthesis. DHDIBBA is easily obtained by the iodination of DHBBA. These compounds are also found when erythrosine is heated in excessive alkali. The results of the Ames test using DHBBA and DHDIBBA showed they did not possess mutagenic activity. The results clearly demonstrated that establishment of an upper limit for DHBBA and DHDIBBA is important in the quality control of fluorescein and erythrosine.